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Convergent Evolution Upends Honeyeaters' Taxonomy
grrlscientist writes in with a beautiful piece of science, beautifully explicated. The poignant bit is that the birds in question are all extinct. "Every once in awhile, I will read a scientific paper that astonishes and delights me so much that I can hardly wait to tell you all about it. Such is the situation with a newly published paper about the Hawai'ian Honeyeaters. In short, due to the remarkable power of convergent evolution, Hawai'ian Honeyeaters have thoroughly deceived taxonomists and ornithologists as to their true origin and identity for more than 200 years."
There have been debates over the taxonomy of odd creatures (with similarities to other known creatures) forever. Sometimes simple physical resemblence just doesn't really tell the tale. Of course, evolution producing similar looking/behaving birds is nothing new either (just look at how similar African parrots and South American parrots are to one another).
The really great debates come when zoologists get into trying to classify an animal that looks like (or behaves like) two DIFFERENT known creatures. One of my personal favorites is the Red Panda. The bottom of its body and claws look like a bear's (you can see it clearly in this picture) and it eats only bamboo, just like a Giant Panda. But the rest of it looks like a raccoon. This cute little furball finally had to be given its own unique family, because no one was quite sure where to put the little bastard. And it's still debatable if it truly deserves its own family.
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Proposed text: "Evolution, like gravity, is just a theory. Please act accordingly."
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The answer is two-fold: money, and existing taxonomies are mostly correct.
Biologists have limited resources, so comprehensive reassessment of the entire tree of life based on genetic analysis is going to get done bit by bit over a long time, and we know we're pretty safe going with what we've got in the meantime.
And while enough genetic analysis has been done to confirm traditional taxonomy on quite a few species, it is only the cases where there is a disagreement that it makes the news. In all the other cases they agree, so traditional taxonomy is left intact.
There are a few dramatic cases like this one, though. There are a couple of species of lizard in the Yucatan that have an extra cervical vertebrae that turn out to have independently evolved that way (I prefer the term "independent evolution" rather than "convergent evolution", as the latter may confuse laypeople into thinking that distinct species have somehow become one.)
In those cases, genetic taxonomy wins, but they are always going to be in the minority.
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Ah, thanks for the kind invitation to join your discussions. i wish i had more time to do so, but alas, i have only a few hours per day of internet access, so i spend most of that time looking for papers to write about and answering emails as well as publishing my essays and images. but i will try to make more of an effort to comment here now and again!
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"Just" a shift in population ratios? Nice attempt to drive a wedge into the non-existent space between "micro-evolution" and "macro-evolution".
For the record:
Shift in population ratios = change in allele frequencies = evolution.
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It only seems to contradict global warming if you have only a superficial understanding of it. "Monotonic increase of temperature" was never a theory of global warming, so because a piece of data contradicts your understanding means nothing.
Also, the moth thing is more an example of natural selection than the evolution of a new trait. We've observed evolution in labs with flies and plants. Again, just because a layman's example and understanding doesn't seem to completely explain the theory, that doesn't mean that's all the understanding or explanation possible.
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Another poster, who is probably a biologist, gave two very good answers to your question; as a bioinformatician, I'll give a third. You're right that DNA doesn't lie, but we can have a damn hard time figuring out what it's trying to tell us. There is no universally agreed-upon method for reconstructing phylogenetic trees from sequence data -- Google on "phylogenetic algorithm" to see the enormous number of methods that people have come up with, and what an active area of research this continues to be. Also, the Linnaean taxonomic system, obviously, was not designed with modern genetics in mind, and trying to shoehorn phylogenetic data into this system (which is pretty much what everybody does, even if they're not happy about it) can lead to bizarre results. Until we have what everyone agrees is really a gold standard method for reconstructing ancestral trees, this is the way it's going to be.
The correlation between ignorance of statistics and using "correlation is not causation" as an argument is close to 1.
Thank you for making this post. It's good to see that someone out there understands this basic concept. Although, as a sister post notes, we do have a pretty good idea as to the cause of gravity.
Law of gravity: Objects attract each other according to their mass and the square of the distance between them. (F = GMm/R^2)
Theory of gravity: Gravity is caused by the interaction of gravitons at the quantum level, making gravity one of the basic forces.
Notice that theories describe the how and why of things, laws make concrete facts about the way things are.
Neither scientific laws or scientific theories (not to be confused with traffic laws or layman's theories, which describe different things entirely) are above being revised. In the case of laws, becoming more precise as our instruments become more precise, for instance, I believe that the universal gravitational constant (G, above) has been changed at various times as we are able to get better measurements. Theories, are often refined, partially revised, or scrapped altogether, often, we will use different theories depending on the model we are using (once again, scientific model, not like a car model, or like a car in general, get your analogies away from me! ;-) ).
The most important distinction between laws and theories, is that laws can be proven: measure the gravitational pull between two masses, if it fits the formula, voila! Gravity still works as predicted, the aprocralypse is not upon us yet. Theories, however, can only be disproven, you can say, "Gravitons cannot be the cause of gravity, here is my evidence, which the theory doesn't explain," but you cannot say, "Here is my proof that gravitons cause gravity." (you can try to get proof, but at most you will have a very strong correlation, which, as every slashdotter is fond of pointing out, does not prove causation.
"But," you say, "that means that everything we know could be a lie!" To which I reply, "Yes, yes it does, but that is unlikely, because most theories that actually have a name, have been shown to correlate with the facts very, very consistently, and although this doesn't prove causation, it's a pretty good indication that most of science is true."
The creator of this post (Jacob Smith) hereby releases it, and all of his other posts, into the public domain.
My favorite example is the Naked Mole Rat. It lives in Africa in underground, and it is a kind of rat. However, as far as mammals go, it's very weird.
First of all, it's completely cold blooded. It cannot regulate its temperature at all. It's also blind and hairless. They have a queen that gives birth , and the others are workers in various castes, such as tunnel-maintainers, guards, or nurses.
So convergent evolution also happens in social structures, not just physiology.
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